A VFD puzzle.

T

TNBen60

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Hello,

Several years back I bought a Soyan Power VFD for the Enco mill. I worked through the users manual and set it up and it has worked like a champ until recently. I can run it for roughly 10 minutes and then it stops with the POFF/UU error. It will then drop out at shorter and irregular interval. I went back to the book and it suggests that the problem is input voltage has dropped out. I measured the voltage and it’s consistently 235 - 240 volts.

I had let the machine sit for a while as I got ready to retire so I figured there might be some corrosion in the power leads. I cleaned everything on the input side with no effect.

Then I noticed something. Every time I use the volt meter to measure the input voltage on the VFD terminal I hear the VFD reset and I’m back in business. I feel kinda stupid trying to use the mill with the voltmeter close at hand to reset the VFD. I’m wondering if I’m missing something?

If I have to I will junk the VFD and get a motor starter to use with the rotary phase converter that came along after the VFD installation but I would rather spend the money on materials.
 
If you are applying pressure to the terminals when you check the voltage then it sounds like a poor connection or the circuit board trace is going. The input side on many of these VFD's is not made to handle the rated current and they can burn or become intermittent. This would explains the intermittent nature of the low voltage error. Capacitors also tend to deteriorate over time. Larger VFD's are worth rebuilding but not the smaller ones. You could take it apart to look at the input power connections,circuit board traces.

You would be better off replacing the VFD with something like the G20 series form Automation Direct, you also will probably get much better performance of your mill at lower Hz due to the sensorless vector drive characteristics. Motor starter and RPC would be a much more expensive proposition.
 
+1! I put an Automation Direct GS20 on my mill. It was super easy to configure and has US support.
 
Agreed, probably a fractured solder joint where the terminals meet the circuit board
Repair could take minutes or hours
 
Thanks guys. I kinda expected that but it never hurts to see if I missed anything. I will start look for a way to plumb it into the rotary phase converter.
 
When you initially setup the VFD did you wire the VFD directly to the motor and bypass all the original controls? If you don't wire the VFD DIRECTLY to the motor and you still use the factory control switch this will cause problems like you are describing. It might work for a while but it will eventually likely kill the VFD... very similar to what you describe.

If you did bypass the factory controls when initially installing the VFD it seems like you will have a bit of rewiring to enable the factory controls when you swap the machine to use your RPC.

The cracked solder joints diagnosis makes a lot of sense. I would try reflowing the solder on the VFD circuit board pads for the power leads.

In the good old days solder had lead in it that allowed some flexibility in soldered joints. When they banned lead in solder cracked solder joints became much more prevalent. Heating and reflowing the solder will usually fix the issue. I guess they are worried about little kids removing circuit boards from equipment and sucking on the solder joints like they were a binkey.

Personally I think the Automation Direct VFD's are way over priced for a home shop. Huanyang GT series VFD's have been excellent VFD's for me and much more economical.
 
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As a descendant of people known for their thriftiness I’ve been accused of following their spending philosophy. OTOH, I have never regretted spending the little extra on the Automation Direct VFD. The instructions alone were worth the extra cost. What I went through on the cheap ENC VFD that came on my lathe only reinforced that opinion. The difference between them is that the ENC is more like an open source device that can be whatever the user wants with enough configuration inputs while the AD VFD was meant to run equipment with a minimum of fuss by ordinary people. Practical Machinist banned discussion of the Huanyang VFDs because so much of the conversation was about problems.
 
I paid $259 for a 10hp Huanyang GT VFD to power my table saw. The comparable DURApulse GS20 VFD from Automation Direct for powering my 10hp table saw is $887... not to mention being back ordered / not currently available. I could buy 3 Chinese Huanyang GT VFD's and have money left over or one GS20... country of origin not easily findable on their page... could that mean also "Made in China"?

For "me" an extra $687 is a lot of money, more than I paid for the sliding table saw the Huanyang is powering.

THE ONLY GOOD ADVICE I EVER GOT FROM "PRACTIAL MACHINIST" was an IM telling me... "Go to Hobby-machinist.com and ask opinions about the mill you are considering buying over there. You will get much higher quality replies!"... which I did... and I did receive much higher quality replies. Practical Machinist loudmouths trash talking Huanyang GT VFD's is about as good of a recommendation for buying a Huanyang GT VFD as I can get... in my experience!

This is a hobby shop forum. I have a hobby shop. I have no production demands. If I were a business and my machinery running meant the difference between feeding my family, and the families of all of my employees, or not I would understand paying a premium for service and support. But I would also have to ask myself... if my $887 (Chinese?) VFD died on me would I be able to get a replacement or would I be sending my workers home until the GS20 I need is back in stock?
 
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I have not experienced any failures on the dozen cheap VFD’s i have in service right now. Some folks are superstitious I suppose
 
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